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The Wonders of Baker’s Yeast

Among life’s simplest joys: smelling freshly baked cinnamon rolls wafting through the kitchen, sliding the tray of artfully coiled pastries from a warm oven, and marveling at their golden crust and fluffy interior. An ideal cinnamon roll features a potent cinnamon-sugar mixture oozing in sticky spirals. It’s often topped with a generous smear of tangy cream cheese icing that’s tempered with notes of orange peel and vanilla, sweet and rich enough to catapult you back to childhood. While the filling and icing are notable qualities, what really makes or break a cinnamon roll is its texture. Cinnamon rolls may simply serve as a vehicle for sugar and icing, but their bready foundation boasts an often-understated value. Imagine greedily lunging for a roll and biting into it, only to discover that it’s a rock-hard spiral of disappointment, instead of an airy and delicate pastry with a tender crumb. The science behind the texture of a perfectly fluffy cinnamon roll lies in the yeast.

Photo credit: Mai Nguyen

When you’re browsing the baking aisle in the grocery store, you may be overwhelmed or confused by the sheer number of different forms of yeast available—you’ll find loose granules in packets and jars, bricks, discs, and fast-rising, instant, or active dry. Despite the multitude of forms the yeasts can come in, they’re all merely purified and processed versions of the same organism. Saccharomyces cerevisiae, or baker’s yeast, is a microorganism used in professional and home kitchens alike primarily as a leavening agent for baked goods (1).

The three most commonly/commercially available forms of yeast are:

  • Caked yeast: This moist block consists of fresh, living cells that are packed tightly together. This form of yeast shows substantially higher leavening activity than its dried forms. Caked yeast is highly perishable and has a shelf life of only one to two weeks. More commonly, you’ll encounter yeast granules in packets or jars, widely available as active dry or instant.
  • Active dry: Active dry is a granular form of yeast that has been dried at high temperatures. These granules are comprised of yeast clusters that are encapsulated in a protective coating of yeast debris that formed on the surface of the granules during the drying process. These yeast cells are dormant and need to be rehydrated in warm water before being used. Simply sprinkle the granules in warm water (around 110°F), stir, and wait five to ten minutes. Water will dissolve the protective coating surrounding the granules, releasing the revived yeast cells from within. As the yeast become active, you should see a foamy layer of bubbles forming at the surface, which is carbon dioxide being released.
  • Instant rapid-rise yeast: Boasting higher viability and increased CO2 production, instant rapid-rise yeast is dried at more gentle temperatures than active dry, so more yeast cells survive this drying step. Bakers can add instant rapid-rise yeast directly to the flour, eliminating the need for prehydration. Because instant rapid-rise yeast produces carbon dioxide more vigorously than active dry yeast, these two forms of yeast should not be used interchangeably.

Granules of active dry yeast
Photo credit: Mai Nguyen

Instant rapid-rise yeast
Photo credit: Mai Nguyen

How does this tiny organism transform a dense blob of dough into a puffy masterpiece? To harness its leavening power, we rely on the phenomenon of fermentation. In the first steps of bread baking, water, yeast, flour, and salt are combined. Kneading hydrates the flour and after just a few minutes of manipulation, the dough becomes noticeably stretchier and more pliable. Water enables individual protein molecules in the dough, glutenin and gliadin, to link together to form long, elastic chains of a protein called gluten. These individual gluten strands combine to form a mesh-like network which gives bread its structure and chewy texture (2). Meanwhile, the addition of water also activates enzymes in the flour known as amylases which break down the flour’s starches into simple sugars, providing food for the yeasts (3).

The yeasts feed on these simple sugars and convert them into ethanol and carbon dioxide gas (CO2). This is where the magic begins. As carbon dioxide is released into the dough, it becomes trapped in the gluten matrix. As more and more CO2 bubbles form, the protein network stretches, inflating the dough. Depending on the recipe, dough can spend between an hour to several days rising and can expand two to four times its original size. This initial rising step is often referred to as bulk fermentation.

Like many other types of yeasted breads, a classic yeast-based recipe for cinnamon rolls calls for two rising steps. After the dough has been kneaded and has undergone bulk fermentation, it’s time to roll out the dough and shape it to prepare it for the second rising step, known as proofing. Many recipes for yeasted breads will instruct you to “punch down” dough after the initial rise. In this step, we turn and fold the dough, fill it with a cinnamon-sugar mixture, shape it into coils, and allow them to rise into bloated versions of their former selves (2). This “punching down” or turning step serves a couple of purposes: it stretches the gluten and expels excess CO2 buildup trapped in the dough from the bulk fermentation step, which can inhibit any further yeast activity. Handling the dough at this stage also redistributes yeast, moisture, heat, and sugars throughout the dough for optimal lift and flavor.

A noteworthy point: while our goal is to encourage yeast proliferation and to optimize the production of CO2 and flavor molecules, bakers should be cautious of overfermentation. If yeast fermentation happens too rapidly or continues for too long, gas bubbles can overinflate and burst, causing our dough to collapse (3). The excess of CO2 can also cause the yeast to leave behind many unwelcome tasting flavor compounds and the bread may end up tasting like alcohol.

In our final phase, our twice-risen dough is placed into the oven. Once inside, the dough experiences one last rise thanks to the high heat. The heat causes CO2 present in the dough to expand and for about the first ten minutes in the oven, the rising temperatures stimulate a rapid burst of activity in the yeast, causing them to produce even more CO2. Water and ethanol byproducts in the dough will also expand during heating. This causes the bread to rise dramatically in the oven a phenomenon known as oven spring (3). Eventually, the CO2 and alcohol are expelled from the bread and the yeast cells succumb to a dry, hot death once temperatures exceed 140°F (2).

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Photo credit: Mai Nguyen

Behind a cinnamon roll—or any kind of yeast bread —lies an intricate chemistry involved in its creation. Without the wonders of yeast and fermentation, bread wouldn’t exist as we know it today.

References Cited

  1. McGee, Harold. On food and cooking: the science and lore of the kitchen. New York: Simon & Schuster, 1997. Print.
  2. Crosby, Guy. The Science of Good Cooking. Brookline, MA: Cook’s Illustrated, 2012. Print.
  3. Bernstein, Max. “The Science of Baking Bread (And How to Do It Right).”Serious Eats. 1 Oct. 2014. Web. 11 Aug. 2015.

Mai NguyenAbout the author: Mai Nguyen is an aspiring food scientist who received her B.S. in biochemistry from the University of Virginia. She hopes to soon escape the bench in pursuit of a more creative and fulfilling career.

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Gluten-free & Egg-free

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Wheat provides about twenty per cent of the world’s calories and more nourishment than any other source of food over the course of human civilization, yet more and more people in in the last few years are coming out as gluten sensitive and moving towards gluten-free alternatives. The question is, should we go gluten-free? In the meantime, start-up companies like Hampton Creek Foods are working on creating more sustainable plant-based foods such as egg-free mayonnaise.
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Engineering the Perfect Gingerbread House

Building gingerbread houses can be a frustrating process. An idyllic three-story building with crystal sugar snow, marshmallow snowmen, and gumdrop twinkle lights can quickly end in a collapsed mess, sending icing windows and candy cane gates into disarray. But don’t resort to those trusty milk cartons and graham crackers just yet – with a few changes in technique, your dream house can easily be obtained.

gingerbread houses

UCLA students built gingerbread houses at a recent Science & Food event

During our recent “Engineering the Perfect Gingerbread House” event, graduate student Kendra Nyberg taught UCLA students about the best practices for gingerbread construction. Her lecture delved into the molecular makeup of the materials and the physics behind the structure.

Base Construction Materials: Gingerbread and Icing

Gingerbread should be sturdy and demonstrate elasticity, which is the measure of its ability to resist deformation [1]. Because the gingerbread walls will be under stress from the roof, there needs to be sufficient resistance to avoid cracking or total collapse. Dough with a tough, springy consistency and decreased moisture content is ideal, and can be achieved by using flour with high protein content, such as bread flour. Higher-protein flours contain more glutenin and gliadin proteins, which create the springy gluten network that gives dough its elastic properties.

gingerbread houses_fig 1

Photo credit: Ionacolor.com

Icing serves as the glue that holds the entire structure together. The mixture should be just pliable enough to hold the gingerbread pieces together before drying into a hard, unmovable substance. Here egg whites are key. When beaten, the egg’s proteins denature and then coagulate, stabilizing air bubbles in the icing and creating white, foamy “peaks” that vary in their stiffness and resistance to gravity. Stiffer peaks are better for gingerbread icing, and more coagulated proteins can contribute to a stronger paste.

gingerbread houses_fig 2

Photo credit: Advanced Materials

Why use icing instead of frosting? Both confections contain copious amounts of sugar, but where icing contains egg whites, frosting typically incorporates butter. The additional fat globules from butter provide some thickness and stability to the frosting. However, since standard buttercream frosting does not contain egg whites, the only proteins present are those from the milk in the form of butter. Although these proteins are perfect for dense and creamy cupcake topping, they do not assemble into the stiff, strong networks needed for gingerbread house construction.

Stability and Height: Architectural design

Once the bricks and mortar of your gingerbread house have been created, you can move onto the creative part of the process – construction. There are many forces acting on a gingerbread house. Consider the roof: forces on the sloping gingerbread roof includes friction from the frosting, a normal force perpendicular to the gingerbread surface, and gravity pulling the roof toward the floor. These forces also show up to varying degrees in all of the upright walls of the gingerbread house. To avoid collapse, it is best to spread out the forces over many surfaces. For example, a wider structure with a flatter rooftop will be sturdier than a narrow house with a sloping roof.

Normal, friction, and gravity forces acting on a gingerbread roof Photo credit: dallassd.com

Normal, friction, and gravity forces acting on a gingerbread roof
Photo credit: dallassd.com

If the height of the house is very high, the gingerbread is also more sensitive to buckling under the added weight of the extra gingerbread. To prevent buckling, you can calculate the critical height at which buckling occurs, which depends on such factors as gingerbread density and the force of gravity [2].

Photo credit: Tim Jones (Zoonomian)

Photo credit: Tim Jones (Zoonomian)

You don’t have to be an engineer or an architect to construct the perfect gingerbread house. With the proper dough, frosting, and design considerations, the house of your dreams can be achieved – perfect to last as a display through the holidays. Now get building!

References cited

  1. Iona (2011) “Elasticity (TV set art) (3).” blog.ionacolor.com
  2. Tim Jones (2013) “Musings on Structural Gingerbread.”

Catherine HuAbout the author: Catherine Hu is pursuing her B.S. in Psychobiology at UCLA. When she is not writing about food science, she enjoys exploring the city and can often be found enduring long wait times to try new mouthwatering dishes.

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Baking Science & Tasting Colors

Science of Baking Infographic

The folks over at Shari’s Berries were kind enough to send us a detailed infographic on baking science. Meanwhile, there are some folks  who can actually taste colors.
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Harnessing Creativity & The Science of Pie (Event Recap)

On your mark…
Get set…
GO!

As the doors swung open, guests eagerly awaiting the final Science & Food lecture series were transported to a place nothing short of a Pie-Palooza. Twenty student teams stood confidently next to their baked confection and explained to the judges how they employed the scientific method to creatively reimagine the art of baking the perfect pie. Some developed aqueous solutions to modify the flakiness of their pie crusts while others sought to improve filling texture by altering pH levels and used techniques such as microscopy to measure their results. Whatever their approach, the students proved that a little bit of science goes a long way in mastering the craft of pie baking.

Dr. Paul Barber (Associate Professor, UCLA) and Dave Arnold carefully evaluate the students pie presentations

Dr. Paul Barber (Associate Professor, UCLA) and Dave Arnold carefully evaluate the student pie presentations

Special guest judges, Nicole Rucker of Gjelina Take Away and food critic, Jonathan Gold

Nicole Rucker (Pastry Chef, Gjelina Take Away) and Jonathan Gold (Food Critic, LA Times) partner up as special guest judges


Lena Kwak and Dr. Rachelle Crosbie-Watson (Associate Professor, UCLA) take a closer look at student posters

Lena Kwak and Dr. Rachelle Crosbie-Watson (Associate Professor, UCLA) take a closer look at student posters

After the large-scale pie tasting, guest speakers, Lena Kwak and Dave Arnold, took the stage to share their insight on innovation in the culinary laboratory and emphasized how unforeseen mishaps often lead to novel discoveries. Co-Founder and President of Cup4Cup, Kwak discussed how her breakthrough formulation of gluten-free flour was a by-product of her fearlessness to try new techniques and make mistakes in the kitchen. Founder of the Museum of Food and Drink (MOFAD) and Owner of Booker & Dax, Arnold described how curiosity and relentless dedication to experimentation led to the development of many of his out-of-the-box culinary gadgets. Case in point: the Searzall, one of his latest inventions designed for hand-held blowtorches to evenly apply high temperature heat to sear foods while avoiding the remnants of unpleasant aromatics. He also invoked the audience to participate in an experiment where he challenged everyone to digest gymnemic acid, which dulls our sensory perception of sweetness. This exercise was designed to help guests unlock and appreciate the other factors (such as texture) that contribute to our understanding of taste.

Kwak addresses the audience's questions and reveals some of ingredients in her gluten-free flour

Kwak addresses the audience’s questions and reveals some of ingredients in her gluten-free flour


Dave Arnold explains his investigative process to developing his newest product, Searzall

Arnold explains and demonstrates the evolutionary process involved in developing the Searzall


Gymnemic acid, a sweetness inhibitor, made this bag of sweets taste completely bland!

Gymnemic acid, a sweetness inhibitor, made this bag of sweets taste completely bland

Finally, the panel of special guest judges shared with the audience their favorite pies from the student entries and awarded the students with prizes for the “Most Creative Pie”, “Most Qualified to Enter a Real Pie Contest”, “Best Scientific Pie”, “The People’s Choice Pie”, and “Best Overall Pie”.

Tom Folker and Eric Hirshfield-Yamanishi take home the "Most Qualified to Enter a Real Pie Contest" prize

Tom Folker and Eric Hirshfield-Yamanishi take home the “Most Qualified to Enter a Real Pie Contest” prize

Folker and Hirshfield-Yamanishi explored the effect alcohol, specifically Fireball whiskey, had on the overall flakiness of their pie crust and produced a pie the judges thought was worthy of a professional pie contest.

The "Most Creative Pie" went to Ying Zhi Lim and Jen So for their rosemary-infused deconstructed apple pie

The “Most Creative Pie” went to Ying Zhi Lim and Jen So for their imaginative apple pie

These creative young women, Lim and So, took the competition to the next level by presenting a deconstructed, rosemary-infused apple pie topped with a “reverse spherified” lemon zest cream cheese sauce to a create a harmoniously balanced and flavorful treat.

Christina Chung, Tori Schmitt, and Elliot Cheung impressed the judges and won the "Best Scientific Pie" award

Christina Chung, Tori Schmitt, and Elliot Cheung impressed the judges and won the “Best Scientific Pie” award

Chung, Schmitt, and Cheung added different combinations of liquids to generate their pie crust and recorded the amount of force required to alter the elasticity of the baked crust. Ultimately, the incorporation of beer into their pie crust recipe significantly altered texture as measured and quantified by the elastic modulus.

Apple Queens, Alina Naqvi and Ashley Upkins-Scott, stole the show and won both "The People's Choice Pie" and  "Best Overall Pie" prize

Apple Queens, Alina Naqvi and Ashley Upkins-Scott, stole the show and won both “The People’s Choice Pie” and “Best Overall Pie” prize

Naqvi and Upkins-Scott of team Apple Queens took different varieties of apples, including Granny Smith, Red Delicious, Pink Lady, and Fiji, to produce a crumble top pie that garnered praise from both the audience and the judges.

Congratulations to all the winners!

All photos were captured by Patrick Tran. For more images from the event, visit this photo album.


Anthony MartinAbout the author: Anthony Martin received his Ph.D. in Genetic, Cellular and Molecular Biology at USC and is self-publishing a cookbook of his favorite Filipino dishes.

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Gluten Sensitivity & Gluten-Free Baking

glutenfreecookies

This week we’re all about gluten. NPR summarizes recent research on gluten sensitivity, while America’s Test Kitchen gives NPR the lowdown on gluten-free baking. Read more

Gluten Tolerance

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photo credits (whatsername?/flickr)

It seems that people love to hate gluten. Though it plays an important role in baking, gluten has a bad reputation. The market for gluten-free foods and beverages reached $4.2 billion in 2012; an increase of 28% since 2008.[1] It is actually difficult to go into Whole Foods and find a baking mix with gluten. But gluten isn’t necessarily bad; it’s just misunderstood. Have a heart, and let’s learn to better appreciate gluten for the remarkable protein network that it is.

Gluten is comprised of two proteins; gliadin and glutenin, that are conjoined with starch in the endosperm of various grass-relatedgrains. Endosperms of flowering plants are stored with protein to nourish embryonic plants during germination.[2] True gluten is typically defined as coming only from certain members of the grass family, namely wheat, but gluten may arise from other cereal grains, like barley and rye, as they also contain protein composites of similar proteins. When water and flour mix, glutenin molecules cross-link with gliadin, and form a sub-microscopic gluten network. Stirring and kneading help gluten stretch and organize into a stronger network, turning simple paste into dough. If dough is leavened with yeast, the fermenting microbes produce carbon dioxide bubbles that are trapped within the gluten network and cause the dough to rise. Baking dehydrates the dough as the protein foam structure solidifies.

The development of gluten affects the texture of baked goods. Kneading promotes the formation of gluten strands and cross-links, creating baked products that are chewier the longer you knead the dough, such as pizza crust and bagels. Less developed gluten yields tender pastry products. For this reason, bread flours are high in gluten, while pastry flours have a lower gluten content. When a tender, flaky product is desired, like a pie crust, a fat such as shortening can be used to inhibit cross-link formation, along with less kneading and low moisture content.

photo credits (Andrea_Nguyen/flickr)

photo credits (Andrea_Nguyen/flickr)

Gluten intolerance has recently become a very talked-about condition. The most prominent form of intolerance occurs in people with Celiac disease. When people with this disease eat foods containing gluten, their immune system produces antibodies, which damage the intestinal lining, causing inflammation and nutrient malabsorption. The cause of the disease is currently unknown. Some gene mutations seem to increase risk of developing Celiac, but not everyone with the mutation is gluten intolerant. A study published in the American Journal of Gastroenterology states that the prevalence of Celiac disease in the US is 0.71%. [4] Recently, another potential form of intolerance called non-celiac gluten sensitivity has garnered attention. After consuming gluten, people with gluten sensitivity may experience diarrhea, fatigue and joint pain, but their intestines are not damaged as would be in the case of Celiac. In 2011, this condition was lent credibility by Peter Gibson, a professor of gastroenterology at Monash University and director of the GI Unit at The Alfred Hospital in Melbourne, Australia, who published a study that found gluten to cause gastrointestinal distress in patients without Celiac disease.[5] The experiment was one of the strongest pieces of evidence to date that non-celiac gluten sensitivity is a genuine condition. However, his study had not revealed why his subjects reacted adversely to gluten. He resolved to rigorously repeat the trial, ensuring that no confounding factors affected the results.

The study was conducted as follows: A total of 37 subjects, all meeting the criteria for having non-celiac gluten sensitivity were provided every meal for the entire study period. Any and all potential dietary triggers were removed, including lactose, certain preservatives, and fermentable, poorly absorbed short-chain carbohydrates, also known as FODMAPs. They were first fed a baseline diet low in FODMAPs for two weeks, then were given one of three diets (high gluten, low gluten, or placebo). Each subject cycled through each diet, and none ever knew what specific diet he or she was eating.

Regardless of which diet they were on, subjects reported similar degrees of worsened gastrointestinal ailments. Their reported pain, bloating, nausea, and gas all increased over the baseline diet. The data clearly indicated that a nocebo effect was occurring – in other words, participants were experiencing an entirely psychological phenomenon in which a harmless substance causes a harmful effect.

"A celiac looking in the window of a Parisian boulangerie." photo credits (justmakeit/flickr)

“A celiac looking in the window of a Parisian boulangerie.” photo credits (justmakeit/flickr)

So whether you eat gluten, cannot eat gluten, or choose to avoid it, it is a scientifically interesting substance that has spurred quite a bit of talk and research. Perhaps gluten is damages us psychologically more than it does health-wise. Despite the possibly nocebic effects of gluten, the booming popularity of gluten-free products has allowed people with Celiac a much greater range of food options, and has encouraged people to examine the ingredients of their foods more closely, though they may be avoiding the wrong substance.

Sources

1. “Gluten-Free Foods and Beverages in the U.S., 4th Edition.” : Market Research Report. N.p., n.d. Web. 31 May 2014.

2. Castro, By Joseph. “What Is Gluten?” LiveScience. TechMedia Network, 17 Sept. 2013. Web. 28 May 2014.

3. “Celiac Disease.” Web log post. Webmd.com. N.p., n.d. Web.Pomeroy, Ross. “Non-Celiac Gluten Sensitivity May Not Exist.” RealClearScience. N.p.,

4. Rubio-Tapia, A., JF Ludvigsson, TL Brantner, JL Murray, and JE Everheart. “The Prevalence of Celiac Disease in the United States.” National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web. 25 May 2014.

5. Biesiekierski JR, Peters SL, Newnham ED, Rosella O, Muir JG, Gibson PR. “No effects of gluten in patients with self-reported non-celiac gluten sensitivity after dietary reduction of fermentable, poorly absorbed, short-chain carbohydrates.” Gastroenterology.


Elsbeth SitesAbout the author: Elsbeth Sites is pursuing her B.S. in Biology at UCLA. Her addiction to the Food Network has developed into a love of learning about the science behind food.

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5 Things About Baking

At our 2013 Science of Pie event, Christina Tosi, Zoe Nathan, and the fantastic students from the Science & Food undergraduate course taught us all about pies, baking, creativity, and the scientific process. We just can’t get enough pie science, so here are 5 fun facts related to baking and some of our favorite baking ingredients:

Baking5


Baking1


Baking2


Baking3


Baking4


Liz Roth-JohnsonAbout the author: Liz Roth-Johnson is a Ph.D. candidate in Molecular Biology at UCLA. If she’s not in the lab, you can usually find her experimenting in the kitchen.

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The Science of Cookies

How would you describe your perfect chocolate chip cookie? Thin and chewy? Ultra-crispy? Thick and cakey? Whatever your preference, knowing how to manipulate the ingredients in a basic cookie recipe is the first step toward chocolate chip cookie bliss. At last week’s “Science of Cookies” student event, graduate student Kendra Nyberg showed us how to achieve two very different cookie textures by riffing off of the classic Toll House chocolate chip cookie recipe.

ScienceofCookies

Cookies wait to be tasted (left) while Kendra explains how gluten makes cookies chewy (right)

ScienceofCookies2

Thin, chewy cookies (left) and thick, soft cookies (right)

Thin, Chewy Cookies from Smitten Kitchen
These cookies are all about moisture. A wetter cookie dough spreads more during baking, creating a much thinner cookie. Extra moisture also promotes gluten development in the cookie dough, creating a slightly denser, chewier cookie. This recipe from Smitten Kitchen maximizes moisture content by using melted butter, less flour, less egg white (which can dry out cookies), and a higher brown-to-white sugar ratio (brown sugar can help retain moisture) than the classic Toll House Recipe.

ThinChewyCookieRecipe

Thick, Soft Cookies from My Baking Addiction
Where the previous cookies craved moisture, this recipe from My Baking Addiction removes extra moisture to create thicker, less chewy cookies. Increasing the flour content and using extra cold butter creates a drier dough that spreads less easily in the oven; adding baking powder to the dough lends extra fluffing power. The reduced moisture in this dough also limits gluten formation for a slightly softer (less chewy) cookie.

ThickSoftCookieRecipe

Of course, this is barely the tip of the cookie engineering iceberg. There are so many ways to tweak a cookie recipe to achieve different textures. In addition to this brief introduction, the internet is full of great resources for cookie hacking. This particularly handy guide from Handle the Heat clearly show some of the ingredient manipulations described above. If you end up experimenting with your favorite cookie recipes, be sure to tell us about it in the comments below!


Liz Roth-JohnsonAbout the author: Liz Roth-Johnson is a Ph.D. candidate in Molecular Biology at UCLA. If she’s not in the lab, you can usually find her experimenting in the kitchen.

Read more by Liz Roth-Johnson


Boozy Apple Pie

On foraging for local ingredients in your college dormitory…

Our Judge’s Favorite winner of the 2013 Science of Pie event showed how beer and vodka affect pie crust color and texture. But they weren’t the only students who experimented with alcohol in their pies. Two other teams—Team Super Rum and the Beam Team—also used alcohol to create flaky, tender crusts. The Beam Team even added Kentucky bourbon whiskey (Jim Beam, of course) to their pie filling for an extra punch of flavor.

So why all the alcohol? According to the Beam Team:

“Our group was inspired by Alex Atala’s process of going out into the Amazon Forest and finding local plants to use as ingredients. As college students, we decided that our ‘native’ ingredient is alcohol since it is easily found in abundant quantities all around us, so we used our two favorite types of hard alcohol: whiskey and vodka.”

There’s another (more scientific) reason for boozing up a pie crust: alcohol creates a more tender, flaky crust than can be easily achieved with water alone. This happens because alcohol and water have very different effects on the formation of springy gluten networks in pie dough.

Gluten develops when two wheat proteins in flour, glutenin and gliadin, are mixed with water. Because parts of these proteins do not like to interact with water, the proteins begin to stick to each other much in the same way oil droplets come together when suspended in water. As a flour-water dough is mixed, the glutenin and gliadin molecules interact to form an extensive elastic network [1].

Gluten development during dough formation. Scanning electron micrographs of gluten networks during early (A), middle (B), and late (C) stages of dough mixing [2]. The development of these gluten networks requires water.

While gluten networks are great for chewy bread dough, they are less than ideal for flaky, tender pie crust. An ideal pie dough has as just enough gluten to hold everything in the dough together. And while gluten development can be minimized by adding only scant amounts of water and handling the dough as little as possible, this is easier said than done.

A more practical solution is to replace some of the water with a liquid that does not promote gluten formation. Unlike water, alcohol inhibits gluten formation. By interacting with the gluten proteins, alcohol molecules limit their ability to stick to each other and form springy networks [1]. Using alcohol in the place of water allows more liquid to be added to the dough while still restricting gluten formation. This results in a softer, more pliable dough that becomes tender and flaky when baked.

TeamSuperRum

Team Super Rum serves their pie and presents their work at the Science of Pie even (left). Test pies made with rum pie crust (top right) or bourbon apple filling (bottom right).

Like the recipe below, the Beam Team paired a vodka pie crust with a decadent bourbon and apple filling. Although vodka is typically used for its subtle flavor, any type of alcohol will prevent gluten formation. As their name suggests, Team Super Rum used rum instead of vodka to create a flaky and uniquely flavored crust. And we bet there are many more delicious possibilities in the realm of alcohol-based pie crusts. If you try this recipe with something other than vodka, share your new pie crust concoction with us in the comments below!


Foolproof Vodka Pie Crust

Cook’s Illustrated, November 2007

2 1/2 cups (12 1/2 ounces) unbleached all-purpose flour
1 tsp table salt
2 tbsp sugar
12 tbsp (1 1/2 sticks) cold unsalted butter, cut into 1/4-inch slices
1/2 cup cold vegetable shortening, cut into 4 pieces
1/4 cup cold vodka
1/4 cup cold water

Process 1 1/2 cups flour, salt, and sugar in a food processor until combined, about 2 one-second pulses. Add butter and shortening and process until homogeneous dough just starts to collect in uneven clumps, about 15 seconds (dough will resemble cottage cheese curds and there should be no uncoated flour). Scrape bowl with rubber spatula and redistribute dough evenly around processor blade. Add remaining cup flour and pulse until mixture is evenly distributed around bowl and mass of dough has been broken up, 4 to 6 quick pulses. Empty mixture into medium bowl.

Sprinkle vodka and water over mixture. With rubber spatula, use folding motion to mix, pressing down on dough until dough is slightly tacky and sticks together. Divide dough into two even balls and flatten each into 4-inch disk. Wrap each in plastic wrap and refrigerate at least 45 minutes or up to 2 days.


Bourbon Apple Pie Filling

2 tbsp all-purpose flour
6 or 7 apples, mix of tart and sweet
1/3 cup sugar
1/2 tsp cinnamon
1/2 tsp nutmeg
1/4 tsp salt
1/2 cup bourbon whiskey
2 tbsp lemon juice
2 tbsp butter cut into small pieces

Preheat oven to 425. Place bottom crust in pie plate.

Peel, core, and halve the apples. Cut into 1/4-inch thick slices, about 7 or 8 cups.

In a 4 quart saucepan, whisk together sugar, flour, cinnamon, nutmeg, and salt. Whisk in bourbon whiskey and lemon juice until evenly blended. Cook over medium heat, whisking frequently until the mixture boils and thickens slightly. Add apples and stir until evenly coated. Continue cooking, stirring continuously, for 3 minutes. Set aside to cool, stirring once or twice for 20 minutes.

Pour apple mixture into the pie shell, mounding apples slightly in the center. Dot with butter and add the top crust. Cut several steam vents into top crust.

Bake 25 minutes at 425. Reduce temperature to 350 and bake 45 minutes longer or until crust is brown and juices are bubbling.

Serve warm or chilled with whipped cream or ice cream.


Online Resources

  1. Pie crust recipe from Cook’s Illustrated via Serious Eats
  2. Bourbon apple pie filling recipe adapted from Group Recipes


References Cited

  1. Technology of breadmaking (2007). 2nd ed. New York: Springer. 397 p.
  2. Amend T (1995) The mechanism of dough forming: Efforts in the field of molecular structure. Getreide Mehl Brot 49: 359–362.

Liz Roth-JohnsonAbout the author: Liz Roth-Johnson is a Ph.D. candidate in Molecular Biology at UCLA. If she’s not in the lab, you can usually find her experimenting in the kitchen.

Read more by Liz Roth-Johnson